It has long been known that UV–Vis/near-IR absorption spectra of
chemical compounds especially colorants influenced by the solvent
media. Therefore the absorption spectra of the colorant materials in solution depend strongly on the solvent–solute interactions (charge–dipole, dipole–dipole, dipole–induced dipole and induced dipole–induced dipole) and solvent nature [30,31]. In order to study of solvent
effects on spectral features of the prepared dyes 3a–e, we recorded their
absorption spectra in solvents with different polarity at a concentration
of 10−4–10−5 M at room temperature. The results are shown in Table 1.
Typical UV–vis absorption spectra of synthesized dyes 3a–e in methanol
(10−4 M) are shown in Fig. 2.